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Old 24th April 2011, 08:25 PM   #1
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Default Test Equipment

What the heck kind of equipment are you guys using to test this stuff out?

Can you guys give us a quick rundown on how you go about testing your new designs and what equipment you use?

Thanks!
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Old 24th April 2011, 09:42 PM   #2
jaycee is offline jaycee  United Kingdom
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An oscilloscope and a signal source are the bare minimum i think. Oh and a multimeter naturally. More than one is handy.
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Old 24th April 2011, 09:49 PM   #3
effebi is offline effebi  Italy
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Quote:
Originally Posted by jaycee View Post
An oscilloscope and a signal source are the bare minimum i think. Oh and a multimeter naturally. More than one is handy.
Ok, that's the basis.
But then? I would like to know how people here get to measure about let's say distorsion , THD, TIM, Pass Band(i.e Gain), Phase.
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Old 24th April 2011, 11:22 PM   #4
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Yea I'm wondering how you guys pump out these awesome FFT graphs and get the measurements effebi mentioned.

I have a 1MHz signal generator, Fluke DMM as well as several chinese DMM's and some analog meters. I also have a 100MHz analog scope and a 50MHz DSO.

I know a few members use some pro DAC units to produce their test frequencies like the DAC1 PRE and I presume they have some equally pricy ADC equipment. Is their software that you use to measure your setup with a patch cord then measure your test subject and it will give you the response of just the unit under test?
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Old 25th April 2011, 12:00 AM   #5
Apex Jr is offline Apex Jr  United States
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Also think a variac is a must too

Steve
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Old 25th April 2011, 10:41 AM   #6
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My suggestions:-

Bench power supply.
At least a couple of DMMs (you can never have too many DMMs)
Analogue oscilloscope.
Low distortion signal generator. (Two will be required for IMD measurements)
Distortion and/or wave analyser. (I've got both)
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Old 25th April 2011, 11:07 AM   #7
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by effebi View Post
Ok, that's the basis.
But then? I would like to know how people here get to measure about let's say distorsion , THD, TIM, Pass Band(i.e Gain), Phase.
Gain and phase measurements, pass band (frequency response) can all be done accurately with a scope and generator. Same for rise/fall times etc.

I think many quote distortion measurements and so on direct from running simulations of the design rather than actual real world measurements on the finally constructed article.

The equipment to measure distortion and so on down to 0.00xxx levels etc doesn't come cheap... and using PC USB "add ons" just doesn't cut it
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Old 25th April 2011, 01:26 PM   #8
effebi is offline effebi  Italy
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Originally Posted by Mooly View Post
Gain and phase measurements, pass band (frequency response) can all be done accurately with a scope and generator.
So you mean for frequency response you input say, a 1 V RMS at 10 Hz, measure the output, then set it 20 Hz, measure the output, .......100Hz, 200Hz.....1000 Hz and so on. Then plot the measured points on a nice Excel logarimic graph, and you are done?
That is it?
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Old 25th April 2011, 03:07 PM   #9
jcx is offline jcx  United States
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Default better soundcards are quite capable

better soundcards with 24/192 ADC easily reach 0.001% THD and IMD and the Nyquist frequency of 96 KHz fits well with traditional "audio analyziers" 80 KHz THD measurement bandwidth

with indirect IMD techniques you can push nonlinear distortion resolution down to the spot noise floor - often as good as -130 dB with 1 second averaging

check RMAA loopback on ESI Juli@ or ASUS Xonar Essence STX

the "accuracy" of 'scope measurements can't compare - but the 'scope and signal generator are required for looking for stability, HF performance issues

Last edited by jcx; 25th April 2011 at 03:35 PM.
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Old 25th April 2011, 03:16 PM   #10
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That's it basically. You want a constant voltage undistorted signal going into the amp. You can use 1/2-octave steps or whatever, but of course the more measurements the more accurate the plot. You don't need a scope necessarily for gain and FR; an AC voltmeter with its own proper freq response can be used.
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